RESULTS OF VERJBITSKI'S EXPERIMENTS
A very important series of experiments bearing directly on this subject was made in 1902 and 1903 by Dr. D.T. Verjbitski. The paper giving the results of this work was not published in any scientific journal until 1908 when the Advisory Committee published it in one of their reports. The experiments were so well planned and executed and the results so definite that I think it is worth while to give in full his summary of results. The bugs referred to are bedbugs.
"(1) All fleas and bugs which have sucked the blood of animals dying from plague contain plague microbes.
"(2) Fleas and bugs which have sucked the blood of animals which are suffering from plague only contain plague microbes when the bites have been inflicted from 12 to 26 hours before the death of the animals, that is, during that period of their illness when their blood contains plague bacilli.
"(3) The vitality and virulence of the plague microbes are preserved in these insects.
"(4) Plague bacilli may be found in fleas from four to six days after they have sucked the blood of an animal dying with plague. In bugs, not previously starved or starved only for a short time (one to seven days), the plague microbes disappear on the third day; in those that have been starved for four to four and one-half months, after eight or nine days.
"(5) The numbers of plague microbes in the infected fleas and bugs increase during the first few days.
"(6) The fæces of infected fleas and bugs contain virulent plague microbes as long as they persist in the alimentary canal of these insects.
"(7) Animals could not be infected by the bites of fleas and bugs which had been infected by animals whose own infection had been occasioned by a culture of small virulence, notwithstanding the fact that the insects may be found to contain abundant plague microbes.
"(8) Fleas and bugs that have fed upon animals which have been infected by cultures of high virulence convey infection by means of bites, and the more certainly so the more virulent the culture with which the first animal was inoculated.